CN113842792A

CN113842792A - Asymmetric PES (polyether sulfone) filter membrane for virus removal and preparation method thereof

Info

Publication number: CN113842792A
Application number: CN202111098240.6A
Authority: CN
Inventors: 贾建东; 卢红星
Original assignee: Hangzhou Cobetter Filtration Equipment Co Ltd
Current assignee: Hangzhou Cobetter Filtration Equipment Co Ltd
Priority date: 2021-09-18
Filing date: 2021-09-18
Publication date: 2021-12-28
Also published as: WO2023040973A1; JP2024534972A; CN115487695B; CN115487695A; US20240207794A1

Abstract

The invention provides an asymmetric PES filter membrane for virus removal and a preparation method thereof, wherein the PES filter membrane comprises a main body, a non-directional tortuous passage is arranged in the main body, one side surface of the main body is a first outer surface, the average pore diameter of the first outer surface is 150-450nm, and the PES filter membrane is a macroporous membrane; the other side surface of the main body is a second outer surface, the average pore diameter of the second outer surface is 10-42nm, and the second outer surface is a small pore surface; the average pore size of the main body continuously changes in a gradient manner from a region on one side close to the first outer surface to a region on one side close to the second outer surface; the main body comprises a pre-filtering layer and a separation layer for intercepting viruses, and the other side of the pre-filtering layer and the other side of the separation layer are transited by continuous fibers; the PES filter membrane is prepared by only one casting membrane solution, is integrally formed, does not need to be compounded, and has a relatively simple preparation process; meanwhile, the prepared PES filter membrane has a strong interception effect on parvoviruses with the particle size of 20nm or more, and can obtain a high protein yield, so that the requirements of practical application are met.

Description

Asymmetric PES (polyether sulfone) filter membrane for virus removal and preparation method thereof

Technical Field

The invention relates to the technical field of membrane materials, in particular to an asymmetric PES (polyether sulfone) filter membrane for virus removal and a preparation method thereof.

Background

The membrane technology is a new technology of modern high-efficiency separation, and compared with the traditional technologies of distillation, rectification and the like, the membrane technology has the advantages of high separation efficiency, low energy consumption, small occupied area and the like, and the core of the membrane separation technology is a separation membrane. Wherein the polymer filter membrane is a separation membrane which is prepared by taking an organic high molecular polymer as a raw material according to a certain process; with the development of the petroleum industry and science and technology, the application field of polymer filter membranes is continuously expanded, and the currently applied fields include gas separation, seawater desalination, ultrapure water preparation, sewage and waste treatment, artificial organ manufacturing, medicine, food, agriculture, chemical industry and the like.

According to the difference of the types of high molecular polymers, the polymer filter membrane can be subdivided into a cellulose polymer filter membrane, a polyamide polymer filter membrane, a sulfone polymer filter membrane, a polytetrafluoroethylene polymer filter membrane and the like; in addition, the membrane may be classified into a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane and a reverse osmosis membrane according to the pore size of the membrane.

In recent years, in addition to human blood-derived plasma fractionation preparations, countermeasures for improving virus safety are also required for biopharmaceuticals; therefore, pharmaceutical manufacturers have studied the introduction of a virus removal/inactivation step into the manufacturing process; the virus removal method in which filtration is performed using a virus removal membrane is an effective method for reducing viruses while not denaturing useful proteins.

For example, chinese patent CN1759924B (EMD millipore applications) discloses a multilayer composite ultrafiltration membrane (fig. 17) comprising at least one first porous membrane layer having a first face and an equivalent second face, and at least one second porous membrane layer having an equivalent first face and second face, the first layer being superimposed with the attachment of the second layer and having a porosity attachment transition region from the equivalent first face of the second layer to the equivalent second face of the first layer, wherein at least one of the layers is an asymmetric ultrafiltration membrane; the membrane structure formed by compounding has stronger interception effect on parvovirus, and can obtain higher protein yield, thereby meeting the requirements of practical application;

the composite ultrafiltration membrane, however, can only be made using at least two different casting solutions, the composite process being co-casting the two solutions using a slot die coater (schematic apparatus: FIG. 18), adjusting the cast thickness of the first polymer solution to the appropriate thickness, adjusting the cast thickness of the second polymer solution to the final layer thickness of 15 microns or about 10% of the total film thickness, the forming conditions being selected so that the first solution is rapidly heated above the cloud point on the casting drum before immersion in a water bath at 55 ℃ while the second solution has not yet reached its cloud point; such that the first polymer solution forms a microporous layer and the second polymer solution forms an ultrafiltration layer; the preparation of various membrane casting solutions is relatively complicated, the composite process is complex, and the economic cost is high, so that the development of virus removal membranes is limited to a certain extent.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide an asymmetric PES filter membrane for virus removal and a preparation method thereof, wherein the PES filter membrane is prepared by only one casting membrane solution, is integrally formed, does not need to be compounded, and has a relatively simple preparation process; meanwhile, the prepared PES filter membrane has a strong virus interception effect, and can obtain a high protein yield, so that the requirements of practical application are met;

in order to achieve the purpose, the invention provides the following technical scheme: an asymmetric PES filter membrane for removing viruses comprises a main body, wherein the main body is internally provided with a non-directional tortuous passage, one side surface of the main body is a first outer surface, the other side surface of the main body is a second outer surface, the average pore diameter of the first outer surface is 150-450nm, and the average pore diameter of the second outer surface is 10-42 nm;

the average pore size of the main body continuously changes in a gradient manner from a region on one side close to the first outer surface to a region on one side close to the second outer surface;

the main body comprises a pre-filtering layer and a separation layer for intercepting viruses, wherein one side of the pre-filtering layer is a first outer surface, and one side of the separation layer is a second outer surface; the other side of the pre-filter layer and the other side of the separation layer are transited by continuous fibers.

In the main membrane structure of the PES filter membrane provided by the invention, the sizes of the apertures of the holes on the two outer surfaces of the filter membrane are different and have a certain difference; the pore diameter of the pores on one outer surface is larger, the outer surface with the larger pore diameter is called as a first outer surface in the invention, namely the first outer surface is a macroporous surface of the filter membrane, the average pore diameter of the first outer surface is 150-450nm, preferably, the average pore diameter of the first outer surface is 200-400nm, and the existence of the macroporous surface is beneficial to improving the integral filtering speed of the membrane, so that the fluid filtering time is shorter and the time cost is lower;

the pores on the other outer surface of the filter membrane are smaller in diameter, and the outer surface with smaller pore diameter is called a second outer surface in the invention, namely the second outer surface is a pore surface of the filter membrane, the average pore diameter of the second outer surface is 10-42nm, and preferably, the average pore diameter of the second outer surface is 14-35 nm; the existence of the small pore surface is beneficial to improving the filtration precision of the membrane, and ensures that the PES filter membrane has higher retention effect on parvovirus; the average pore size between the first outer surface and the second outer surface is different and has a certain difference, which indicates that the PES filter membrane is an asymmetric membrane, so that the integral membrane has a higher filtering speed, a larger pollutant carrying capacity and a longer service life; but also can ensure that the parvovirus (particularly the parvovirus with the grain diameter of about 20 nm) has stronger trapping capacity and meets the requirement of practical application;

and through observing the membrane main body structure, the continuous gradient change of the main body average pore size from the area close to the first outer surface side to the area close to the second outer surface side is also found, namely the membrane main body average pore size is gradually changed slowly without mutation, thereby proving that the PES filter membrane is integrally formed without processes such as compounding; the whole filter membrane main body is mainly divided into two areas in the thickness direction, wherein one area is a pre-filtering layer comprising a first outer surface, the pore diameter of an inner hole of the pre-filtering layer is relatively large, the pre-filtering layer is mainly used for intercepting large-particle impurities in fluid, and the pre-filtering layer has large pollutant carrying capacity and high flow speed; the other area is a separation layer containing a second outer surface, the pore diameter of the inner pores is relatively small, and the separation layer is mainly used for intercepting fine particle impurities such as parvovirus in protein, so that the high virus trapping capacity of the filter membrane is ensured, and the PES filter membrane is particularly suitable for being used as a virus removal membrane;

furthermore, the other side of the pre-filter layer (the side of the pre-filter layer facing away from the first outer surface) and the other side of the separating layer (the side of the separating layer facing away from the second outer surface) transition with continuous fibers, it being understood that "continuous" means that substantially all of the fibers are integrally connected to each other, e.g. integrally formed, without the need for additional bonding agents or the like to interconnect them, and the fibers of the network are not separable from each other unless torn by an external force; at the same time, the continuous network-like fibers are interconnected with the first outer surface and the second porous surface; the PES filter membrane is uniform in material, namely the whole membrane is made of PES material, and no change exists in material;

in the context of the present invention, an asymmetric membrane is understood to be a membrane in which the prefiltration layer and the separation layer are both composed of the same material, the two layers being joined to form a unitary structure and being formed directly during the membrane preparation process; in the transition from the prefilter layer to the separation layer, there is only a change in the membrane structure; in contrast, for example, composite membranes, which have a multilayer structure and in which a dense layer as a separating layer is applied in a separate process step to a porous, frequently microporous, support layer or support membrane, the materials of which the support layer and the separating layer are composed often also being different;

the measurement mode of the average pore diameter of the membrane surface can be realized by performing morphology characterization on a membrane structure by using a scanning electron microscope, then performing measurement by using computer software (such as Matlab, NIS-Elements and the like) or manually, and performing corresponding calculation; in the production of the membrane, various characteristics such as the pore size distribution in the direction perpendicular to the thickness of the membrane (the direction is a planar direction if the membrane is in the form of a flat sheet membrane; the direction is perpendicular to the radial direction if the membrane is in the form of a hollow fiber membrane) are substantially uniform and substantially uniform; the average pore size of the whole of the plane can be reflected by the average pore size of a partial region on the corresponding plane. In practice, the surface of the membrane can be characterized by an electron microscope to obtain a corresponding SEM image, and since the pores on the surface of the membrane are substantially uniform, a certain area, such as 1 μm, can be selected²(1 μm by 1 μm) or 25 μm²(5 μm multiplied by 5 μm), the specific area size is determined according to the actual situation, the pore diameters of all pores on the area are measured by corresponding computer software or manually, and then the average pore diameter of the surface is obtained by calculation; of course, the skilled person can also obtain the above parameters by other measuring means, which are only used as reference.

As a further improvement of the invention, the first outer surface is provided with a plurality of first holes in the shape of round holes; the area ratio of the first holes on the first outer surface is 0.1-15%;

the second outer surface is provided with a plurality of second holes in a circular hole shape; the second holes have a hole area ratio of 2% to 10% on the second outer surface.

In the membrane body structure of the PES filter membrane provided by the invention, a certain number of first holes with certain apertures are clearly seen on the first outer surface of the membrane, and the factors such as the aperture size, the number and the shape of the holes of the membrane can generate great influence on the properties such as the filtration precision (interception efficiency) and the membrane flow rate of the membrane; the first holes on the first outer surface are round hole-shaped structures, some first holes are round, and some first holes are oval; and the first holes have a hole area ratio (ratio of first hole area to membrane area) of 0.1-15% on the first outer surface; meanwhile, a certain number of second holes with certain apertures are seen on the second outer surface of the membrane, and the second holes on the second outer surface are also in a circular hole-shaped structure, some of the second holes are circular, and some of the second holes are oval; and the second holes have a hole area ratio (ratio of second hole area to membrane area) of 2% to 10% on the second outer surface; under the mutual synergistic effect between the pore area rate of the first holes on the first outer surface and the pore area rate of the second holes on the second outer surface, the PES filter membrane is ensured to have larger flow velocity, so that fluid can rapidly pass through the porous membrane, the filtering time is shortened, the tensile strength is larger, and the requirements of practical application are met.

As a further improvement of the invention, the average pore diameter variation gradient of the filter membrane is 1.5-6 μm/1 μm; the ratio of the average pore size of the first outer surface to the average pore size of the second outer surface is 7-23.

In the invention, the aperture of the holes of the filter membrane is changed in a gradient way along with the thickness, and the aperture is gradually reduced from a large aperture surface to a small aperture surface; the ratio of the average pore sizes of the two outer surfaces can be called an asymmetry factor, and the smaller the value is (the closer to 1), the stronger the symmetry of the two outer surfaces of the filter membrane is; the larger the value, the larger the asymmetry of the two outer surfaces of the filter membrane; the measurement shows that the ratio of the average pore diameter of the first outer surface to the average pore diameter of the second outer surface is 7-23, preferably 10-20, which indicates that the two outer surfaces of the PES filter membrane of the invention are asymmetric but not highly asymmetric; the asymmetry not only ensures that the filter membrane has larger flux and longer service life; the high virus interception efficiency of the filter membrane is ensured, and the actual requirement is met;

because the pore size of the PES filter membrane is changed along with the gradient of the membrane thickness, the speed of the change of the membrane pore size along with the thickness is reflected by the size of the average pore size change gradient, and the larger the value of the change of the pore size is, the faster the change of the pore size is, the smaller the value of the change of the pore size is, the smaller the change of the pore size is; the value can be obtained by (the average pore diameter of the first outer surface-the average pore diameter of the second outer surface)/the thickness, so the unit is mu m (representing pore diameter)/1 mu m (representing thickness), the average pore diameter change gradient of the filter membrane in the invention is 1.5-6 mu m/1 mu m, and the change gradient value is smaller, which shows that the pore diameter of the filter membrane in the invention changes along with the thickness in a small gradient way, the pore diameter of the membrane cannot change too fast, and overlarge pores do not exist (when the pores of the pre-filter layer are overlarge, the integral mechanical strength of the membrane is too low, the membrane is not pressure-resistant, and the membrane is easy to damage under the pressure action), so the pre-filter layer can play a certain supporting role on the separation layer at the moment, the integral membrane has good mechanical strength and is pressure-resistant, and is not easy to damage under the larger pressure; and can guarantee the high-efficient interception of membrane to the virus, the filter membrane still has faster flux, and has great stain receiving capacity.

As a further improvement of the invention, the PMI average pore diameter of the filter membrane is 15-25nm, the thickness of the filter membrane is 40-150 μm, and the porosity is 70-85%.

The average pore size of the filter membrane is tested by a PMI pore size tester, the PMI average pore size of the filter membrane is 15-25nm, and the PES filter membrane is ensured to have a strong interception effect on nano-scale parvovirus (even the mouse parvovirus with the particle size of 20 nm) by a tortuous path of a main structure and a certain thickness of the membrane, so that the requirement of practical application can be met, and the PES filter membrane is suitable for being used as a virus membrane;

the thickness of the film can be measured by using a scanning electron microscope to perform morphology characterization on the film structure, and then using computer software (such as Matlab, NIS-Elements and the like) or manually measuring and then calculating; of course, the skilled person can also obtain the above parameters by other measuring means, and the above measuring means is only used for reference; when the thickness of the film is too small, the mechanical strength of the film is low; meanwhile, as the filtering time is too short, effective filtering cannot be carried out; when the thickness of the membrane is too large, the filtration time is too long, and the time cost is too large; the thickness of the PES filter membrane is 40-150 mu m, so that the PES filter membrane not only has higher mechanical strength, but also can be effectively filtered, and has higher filtering efficiency, shorter filtering time and lower time cost;

when the porosity of the membrane is too high, the tensile strength of the membrane is too low, the mechanical property of the membrane is poor, the industrial practical value is low, and the market demand cannot be met; when the porosity of the membrane is too low, on one hand, the flow rate of the membrane is influenced, so that the filtering speed of the membrane is low, the filtering time is long, and the time cost is high; on the other hand, the pollution capacity of the membrane is too low, the service life is too short, the membrane needs to be replaced in a short time, and the economic cost is greatly improved; the porosity of the porous membrane is 70-85%, so that the membrane not only has good tensile strength, but also has high filtering speed, high flow rate, high pollutant carrying capacity, long service life and low economic cost, and can retain more impurity particles.

As a further improvement of the invention, the PMI average pore diameter of the pre-filtering layer is 50-200nm, and the porosity is 75-93%; the thickness of the prefilter layer accounts for 70-90% of the thickness of the membrane.

Compared with the separation layer, the pore diameter of the hole of the pre-filtering layer is larger, and the porosity is also larger; tests show that the PMI average pore size of the pre-filtering layer is 50-200nm (preferably 60-180nm), so that the filter membrane has high flow velocity, and can also play a sufficient role in intercepting large-particle impurities (large-particle-size viruses) without influencing the interception of subsequent parvoviruses; the thickness of the pre-filtering layer accounts for 70-90% of the whole thickness of the membrane, which shows that most areas of the membrane are the pre-filtering layer, and under the combined action of large aperture and high porosity (the porosity of the pre-filtering layer is 75-93%), the whole membrane is ensured to have higher flux, high filtering speed, low time cost, higher dirt receiving capacity and long service life.

Parameters such as PMI average pore diameter, porosity and thickness of the pre-filtering layer can be divided into a separating layer and the pre-filtering layer by tearing the PES filtering membrane, and then the pre-filtering layer is subjected to corresponding parameter test; or the film cross-sectional structure is subjected to morphology characterization by using a scanning electron microscope, and then is measured and measured by using computer software (such as Matlab, NIS-Elements and the like) or manually; of course, the skilled person can also obtain the above parameters by other measuring means, and the above measuring means is only used for reference;

as a further improvement of the invention, the pre-filter layer comprises a skin layer region and a pre-filter region; one side of the skin layer region comprises a first outer surface, the hole area rate of the first holes on the first outer surface is smaller than the hole area rate of the second holes on the second outer surface, and the thickness of the skin layer region is 0.3-3.2 mu m; the first holes have a hole area ratio of 0.15% to 1.5% on the first outer surface.

With a portion of the filter membrane, we have found that there is a region within the pre-filter layer where the number of pores is low and the porosity is low, this region we call the skin region, which is on the side of the pre-filter layer facing away from the separation layer; the largest characteristic of the skin region is that the number of holes is small, and the porosity of the region is low; when the pre-filtering layer of the filter membrane comprises a skin layer area, one side surface of the skin layer area, which is far away from the separating layer, is a first outer surface, the number of first holes on the first outer surface is small, although the average pore diameter of the first holes is still larger, the hole area rate of the first holes on the first outer surface is still smaller than the hole area rate of the second holes on the second outer surface, and the hole area rate of the first holes on the first outer surface is 0.15-1.5% through testing; the existence of the skin layer region is beneficial to improving the tensile strength of the membrane, and simultaneously provides a supporting and protecting function for the separating layer, so that the whole membrane is more pressure-resistant, is not easy to crack and has longer service life; in addition, the measurement shows that the thickness of the skin layer region is 0.3-3.2 μm, and the thickness is smaller, so that the supporting strength of the membrane can be improved, and the integral filtering speed and pollutant carrying capacity of the membrane can be avoided.

As a further improvement of the invention, the average pore diameter of the separating layer is 15-25nm, the porosity is 60-80%, and the thickness of the separating layer is 2-20 μm.

Compared with a pre-filtering layer, the pore diameter of the pores of the separating layer is smaller, and the average pore diameter (PMI average pore diameter) of the separating layer is 15-25nm, so that the PES filtering membrane has higher interception efficiency on impurities with small particle size (particularly parvoviruses with the particle size of 20 nm), the requirement of practical application is met, and the PES filtering membrane is particularly suitable for being applied to the field of virus removal;

the thickness of the separation layer is 2-20 μm, so that the impurity interception efficiency is ensured, the integral membrane is further ensured to have higher flux, the filtration speed is high, and the time cost is low; meanwhile, the porosity of the separation layer is 60-80%, which shows that the separation layer can play a sufficient role in retaining parvovirus, and the service life of the membrane is further prolonged;

the parameters of the separation layer, such as average pore diameter, porosity, thickness and the like, can be obtained by tearing the PES filter membrane, dividing the PES filter membrane into the separation layer and a pre-filtering layer, and then carrying out corresponding parameter test on the separation layer; or the film cross-sectional structure is subjected to morphology characterization by using a scanning electron microscope, and then is measured and measured by using computer software (such as Matlab, NIS-Elements and the like) or manually; in addition, the thickness of the separation layer can also be subjected to interception test by using 20nm colloidal gold as impurity particles, the length of a 20nm colloidal gold interception area in the filter membrane is the thickness of the separation layer, and the specific test method can refer to Chinese patent CN 105980037B-membrane for removing viruses; of course, the skilled person can also obtain the above parameters by other measuring means, which are only used as reference.

As a further development of the invention, the ratio of the mean pore size of the prefilter layer to the mean pore size of the separating layer is from 4 to 13: 1.

the main structure of the PES filter membrane is mainly divided into two areas, wherein the area with relatively larger pore diameter is a pre-filtering layer, and the area with relatively smaller pore diameter is a separating layer; after measurement, the ratio of the average pore diameter of the pre-filtering layer to the average pore diameter of the separating layer is 4-13: 1 (preferably 6-11:1), on one hand, the PES filter membrane is described as an asymmetric membrane, the pore diameter of the pores of the PES filter membrane can change with the thickness, and on the other hand, the pore diameter of the PES filter membrane is described as small gradient change with the thickness, the pore diameter of the PES filter membrane can not change too fast, and no overlarge pores exist, so that the high-efficiency interception of the PES filter membrane on viruses is further ensured, the filter membrane can have higher flux, and the PES filter membrane has higher pollutant carrying capacity.

As a further improvement of the present invention, the pre-filter layer comprises first fibers forming a porous structure, the first fibers being a sheet-like structure; the separation layer comprises second fibers forming a porous structure, and the second fibers are in a strip-shaped structure; the first fibers have an average diameter greater than an average diameter of the second fibers, and the second fibers have an average diameter of 30 to 75 nm.

In the membrane body structure of the PES filter membrane provided by the invention, the fiber structure can be clearly seen to be changed along with the membrane thickness, the first fibers in the pre-filter layer are of a sheet structure, and the second fibers in the separation layer are of a strip structure; the average diameter of the first fibers is larger than that of the second fibers, because the holes of the pre-filtering layer are relatively large, the holes formed by the thick first fibers have high stability and are not easy to collapse or shrink, and the stability of the flow rate of the fluid is further ensured; meanwhile, the pre-filtering layer formed by the first fibers of the flaky structure is more stable and pressure-resistant, can play a certain supporting and protecting role on the separation layer, and the distribution of the flaky fiber structure can help fluid diffusion and improve the interception effect of the small holes; the separation layer formed by the second fibers with the strip-shaped structures has proper porosity and pore distribution, so that the whole membrane has high flow rate and high virus interception efficiency; in addition, the average diameter of the second fibers is 30-75nm, so that the stability of holes in the separation layer is ensured, and the parvovirus impurities can be well retained; with the structure, the thick and thin first fibers and the thin and thick second fibers are beneficial to ensuring that the whole membrane has higher mechanical strength and filtration stability, and can be efficiently filtered for a long time; therefore, the PES filter membrane is particularly suitable for being applied to the field of virus removal;

the thickness degree of the fiber section can be regarded as the diameter of the fiber, and the average diameter of the second fiber in the invention can be calculated by using a scanning electron microscope to perform morphology characterization on the cross-sectional structure of the filter membrane and then using computer software (such as Matlab, NIS-Elements and the like) or manually to perform measurement; it will of course be appreciated that the above parameters may also be obtained by other measurement means by a person skilled in the art.

As a further improvement of the invention, the pre-filter layer further comprises a transition region, the transition region is positioned on one side of the pre-filter layer close to the separation layer, the continuous fibers form a porous structure of the transition region, and the continuous fibers gradually change from a sheet structure to a strip structure; one side of the continuous fibers adjacent the separation layer is continuous with one side of the second fibers adjacent the pre-filter layer.

As a further improvement of the invention, the average pore diameter of the transition region is 60-170nm, and the porosity is 75% -82%; the thickness of the transition zone is 4-20 μm.

The PES filter membrane has the characteristics that the size of the membrane pores, the fiber structure and the like of the PES filter membrane are gradually changed along with the thickness instead of sudden change, so that the integral membrane has high mechanical strength, the tensile strength of the membrane is high, and the requirements of practical application can be met; a transition area is arranged on one side of the pre-filtering layer close to the separating layer, and continuous fibers in the transition area form a porous structure of the transition area, so that pores with proper pore sizes and excellent porosity in the transition area are ensured; in the direction of the pre-filtering layer facing the separating layer, the continuous fibers gradually change from the sheet structure to the strip structure; meanwhile, the side of the continuous fibers adjacent to the separation layer is continuous with the side of the second fibers adjacent to the pre-filter layer, and "continuous" means that substantially all of the fibers (continuous fibers and second fibers) are integrally connected to each other, e.g., integrally formed, without being connected to each other using an additional adhesive or the like, and the network-like fibers cannot be separated from each other unless torn by an external force; thus, the PES filter membrane is uniform in material, namely the whole membrane is made of PES material and is integrally formed, and no change exists in material; the average pore diameter of the transition region is 60-170nm, the porosity is 75% -82%, the thickness is 4-20 μm, and under the combined action of the three, the filter membrane is further ensured to have higher trapping capacity for various viruses, and has larger flux, high filtering speed and high economic benefit.

As a further improvement of the invention, the tensile strength of the PES filter membrane is 5-10MPa, and the elongation at break is 8-30%; the flux of the PES filter membrane is more than 600L x h^-1*m^-2@30 psi; the LRV of the PES filter membrane to virus impurities is not lower than 4; the protein yield of the PES filter membrane is not lower than 98%.

Important indexes for evaluating the mechanical strength of the filter membrane are the tensile strength and the elongation at break of the filter membrane; under certain conditions, the higher the tensile strength of the filter membrane is, the better the mechanical strength of the filter membrane is; tensile strength refers to the ability of a film to withstand parallel stretching; when the film is tested under a certain condition, the film sample is acted by a tensile load until the film sample is damaged, and the tensile strength and the elongation at break of the film can be calculated according to the maximum tensile load corresponding to the damage of the film sample, the change of the size (length) of the film sample and the like; tensile strength, elongation at break, can be measured by a universal tensile tester, tensile strength testing methods are well known in the art, for example, tensile strength testing procedures are explained in detail in ASTM D790 or ISO 178; the tensile strength of the filter membrane is 5-10 MPa; the elongation at break is 8-30%, which shows that the filter membrane of the invention has larger tensile strength and elongation at break, better mechanical property and higher industrial practical value, and can completely meet the market demand.

The permeation flux is also called the permeation rate, flux for short, and refers to the amount of substance that a filter membrane passes through the unit membrane area in a unit time under a certain working pressure in the separation process; the flux reflects the speed of the filtration; the higher the flux, the faster the filtration rate of the membrane; the flux of the PES filter membrane is more than 600L x h^-1*m^-2@30psi, its flux is great, indicates that the filtration rate of filter membrane is faster, when guaranteeing to hold back efficiency, and the fluid can rapid through filtration membrane, and the time cost is lower, and economic benefits is higher.

The trapped viruses mainly aim at various viruses with the particle size of 20nm and above (such as mouse parvovirus, the particle size of which is about 20 nm), and the trapped viruses are found through trapping tests, so that the LRV of the PES filter membrane to the various viruses is not lower than 4, which shows that the PES filter membrane has very high trapping rate to the viruses, plays a role in sufficiently retaining virus impurities and meets the requirements of practical application; the yield of the protein of the PES filter membrane is not lower than 98 percent, which indicates that the effective substance protein in the fluid is not easy to be adsorbed on the membrane, on one hand, the membrane hole is not blocked, the filter membrane still has longer service life, on the other hand, the content change of the effective substance protein in the fluid is ensured to be very small, the protein is not basically lost, and the economic benefit is ensured; as a method for testing viral impurities, reference may be made to a membrane for removing viruses of patent-CN 105980037B-, a CN 101816898B-ultrafiltration membrane and a preparation method thereof, a CN 1759924B-ultrafiltration membrane and a preparation method thereof, and the like.

On the other hand, the invention also provides a preparation method of the asymmetric PES filter membrane for virus removal, which comprises the following steps:

s1: preparing a casting solution, and casting the casting solution on a carrier to form a liquid film; wherein the casting solution comprises the following substances in parts by weight: 15-25 parts of polyether sulfone; 55-90 parts of an organic solvent; 6-25 parts of polar additive; the viscosity of the casting solution is 5000-10000 cps;

s2: immersing the liquid film together with the carrier into the curing liquid for at least 10 seconds, wherein the curing liquid invades into the liquid film and gradually diffuses inwards, and then curing to form a separation layer and a pre-filtering layer; the surface energy of the curing liquid is 22-35 dyne/cm; the curing liquid comprises water and a penetration additive with the surface energy not higher than 35 dyne/cm, and the content of the penetration additive is 25-70%; the temperature of the carrier is lower than the temperature of the curing liquid.

As a further improvement of the present invention, the organic solvent is at least one of butyl lactate, dimethyl sulfoxide, dimethylformamide, caprolactam, methyl acetate, ethyl acetate, N-ethylpyrrolidone, dimethylacetamide and N-methylpyrrolidone;

the polar additive is a mixture of glycerol, azodimethyl N-2-hydroxybutyl propionamide and polyvinyl alcohol, and the mass ratio of the glycerol to the azodimethyl N-2-hydroxybutyl propionamide to the polyvinyl alcohol is 2:1: 1.

As a further improvement of the invention, the osmotic additive is at least one of isopropyl alcohol, ethanol and ethylene glycol.

As a further development of the invention, the temperature of the carrier is at least 5 ℃ lower than the temperature of the curing liquid.

As a further improvement of the invention, the temperature of the curing liquid is 25-50 ℃, and the temperature of the carrier is 0-40 ℃.

Preparing a casting solution which comprises a film forming material polyether sulfone (PES), an organic solvent (used for solvent polyether sulfone material) and a polar additive; the polar additive is a mixture of glycerol, azodimethyl N-2-hydroxybutyl propionamide and polyvinyl alcohol, and the addition of the polyvinyl alcohol can control the viscosity of a system, inhibit a liquid film from forming macropores in a phase separation process and effectively improve the stability of the flux of the film; under the synergistic effect of the three substances, the hydrophilicity of the organic solvent can be greatly improved, and the polar solvent is more easily dissolved by the coagulating bath under the combined action of the polar solvent and the coagulating bath during phase separation, so that the polyether sulfone is more easily separated out, and a PES filter membrane with small-aperture gradient change is easily formed; the viscosity of the prepared membrane casting solution is 5000-10000cps, and the viscosity of the membrane casting solution can have great influence on the structure and the performance of the finally formed filter membrane, such as the aperture, the thickness, the flow rate and the like of the filter membrane; such viscosity setting ensures that the finally prepared filter membrane has proper thickness and obtains ideal pore diameter; the viscosity of the casting solution can be directly obtained by a viscometer; then, casting the casting solution on a carrier to form a liquid film; the casting solutions of the present invention may be cast manually (e.g., by pouring, casting, or spreading by hand on a casting surface) or automatically (e.g., poured or otherwise cast on a moving bed); a variety of apparatus known in the art can be used for casting. Casting equipment includes, for example, mechanical coaters, including doctor blades, or spray/pressurized systems. As is known in the art, a variety of casting speeds are suitable, such as casting speeds of about 2 to 6 feet per minute (fpm), and the like, as the case may be;

then the liquid film is immersed into the curing liquid along with the carrier for at least 10 seconds, the phase-splitting curing time is preferably 20-60 seconds, and the proper phase-splitting curing time can be beneficial to obtaining a filter membrane with an ideal membrane aperture size under the combined action of the liquid film casting system; the curing liquid can invade into the liquid film and gradually diffuse inwards, and then the curing liquid is cured to form a separation layer and a pre-filtering layer; in the prior art, the curing liquid is generally water, the mutual solubility of water and an organic solvent is not high, and the phase separation speed is slow, so that the pore diameter of a hole formed at the later phase of phase separation is large, and the condition that the average pore diameter of a pre-filtering layer is large and the asymmetry of a filter membrane is strong can be understood; in order to accelerate the phase separation speed, the surface energy of the curing liquid is 22-35 dyne/cm and is close to the surface energy of the organic solvent by adjusting the curing liquid, so that the curing liquid and the organic solvent can be quickly dissolved mutually, the polyether sulfone is quickly separated out from the organic solvent, and then the filter membrane with small hole diameter and small gradient change is formed; the curing liquid comprises conventional water and also comprises a permeation additive with lower surface energy, the permeation additive can reduce the integral surface energy of the curing liquid and further improve the speed of the curing liquid invading into a liquid film, so that the permeation speed of the curing liquid is increased, the integral phase separation speed of the film is ensured to be higher, macropores are not easy to appear, the integral asymmetry of the film is smaller, and a PES filter membrane with small holes and small gradient and continuous change is easy to form;

in addition, in order to further ensure that the pore diameter of the pores of the membrane changes continuously with small gradients of the membrane thickness, the invention also provides that the temperature of the carrier is lower than the temperature of the curing liquid (preferably, the temperature of the carrier is at least 5 ℃ lower than the temperature of the curing liquid; the temperature of the curing liquid is preferably controlled to be 25-50 ℃ and the temperature of the carrier is preferably controlled to be 0-40 ℃; the arrangement is such that the phase separation speed of the liquid membrane is increased as the temperature difference is larger in relation to the phase separation speed of the liquid membrane in addition to the exchange speed between the solvent and the non-solvent, and the air side of the liquid membrane is formed with small pores first as the curing liquid first enters the air side of the liquid membrane (the side facing away from the carrier), and then large pores are formed on the carrier side of the liquid membrane, and the temperature on the carrier side is lower in relation to the temperature difference, and the pores of the liquid membrane are adjusted by the temperature difference, so that although the side of the membrane carrier forms macropores, the pore diameter of the membrane carrier is not too large, thereby ensuring that a PES filter membrane with small pores and continuously changing gradients is formed.

The invention has the beneficial effects that: the asymmetric PES filter membrane for removing viruses comprises a main body, wherein one side surface of the main body is a first outer surface, the first outer surface is a macroporous surface, the other side surface of the main body is a second outer surface with the average pore diameter of 150-450nm, and the second outer surface is a microporous surface with the average pore diameter of 10-42 nm; the average pore size of the filter membrane is continuously changed in a gradient manner from the area close to the first outer surface to the area close to the second outer surface, and the pore size of the filter membrane is continuously changed in a gradient manner along with the small thickness; the main body comprises a pre-filtering layer and a separation layer for intercepting viruses, wherein one side of the pre-filtering layer is a first outer surface, and one side of the separation layer is a second outer surface; the other side of the pre-filtering layer and the other side of the separating layer are in transition by continuous fibers, the PES filter membrane is integrally prepared and formed by only one casting membrane solution without compounding, and the preparation process is relatively simple; meanwhile, the prepared PES filter membrane has a strong interception effect on parvovirus, can obtain high protein yield, has high flux and high filtering speed, and meets the requirements of practical application; is particularly suitable for the field of virus removal; in addition, the invention also provides a preparation method of the filter membrane, and the preparation method is convenient, quick and effective, simple to operate, green and environment-friendly, and suitable for large-scale popularization.

Drawings

FIG. 1 is a Scanning Electron Microscope (SEM) image of a first outer surface of a PES filter membrane obtained by preparation in example 1, at a magnification of 500 ×;

FIG. 2 is a further magnified Scanning Electron Microscope (SEM) image of the first outer surface of the PES filter membrane obtained in example 1, at a magnification of 2000;

FIG. 3 is a Scanning Electron Microscope (SEM) image of the second outer surface of the PES filter membrane obtained by preparation of example 1, at a magnification of 50K ×;

FIG. 4 is a further magnified Scanning Electron Microscope (SEM) image of the second outer surface of the PES filter membrane prepared in example 1 at a magnification of 100K ×;

FIG. 5 is a Scanning Electron Microscope (SEM) image of a longitudinal section of a PES filter membrane prepared in example 1, wherein the magnification is 700 ×;

FIG. 6 is a Scanning Electron Microscope (SEM) image of a longitudinal section close to the second outer surface of a PES filter membrane prepared in example 1, at a magnification of 50K ×;

FIG. 7 is a Scanning Electron Microscope (SEM) image of a longitudinal section of a PES filter membrane prepared in example 1, taken near the first outer surface, at a magnification of 20K ×;

FIG. 8 is a further enlarged Scanning Electron Microscope (SEM) image of a longitudinal section close to the first outer surface of the PES filter membrane prepared in example 1, at a magnification of 50K ×;

FIG. 9 is a Scanning Electron Microscope (SEM) image of the first outer surface of a PES filter membrane obtained by preparation in example 5 at a magnification of 5K ×;

FIG. 10 is a further enlarged Scanning Electron Microscope (SEM) image of the first outer surface of the PES filter membrane obtained in example 5, at a magnification of 10K ×;

FIG. 11 is a Scanning Electron Microscope (SEM) image of the second outer surface of the PES filter membrane obtained by preparation of example 5 at a magnification of 5K ×;

FIG. 12 is a further enlarged Scanning Electron Micrograph (SEM) of the second outer surface of the PES filter membrane obtained in example 5 at a magnification of 10K ×;

FIG. 13 is a Scanning Electron Microscope (SEM) image of a longitudinal section near the second outer surface of a PES filter membrane prepared in example 5 at 20X magnification;

FIG. 14 is a further enlarged Scanning Electron Microscope (SEM) photograph of a longitudinal section of a PES filter membrane prepared in example 5, taken near the second outer surface, at a magnification of 50K ×;

FIG. 15 is a schematic diagram of a PES filter membrane flux test device according to the invention;

FIG. 16 is a schematic diagram of a testing apparatus for testing the rejection efficiency of a PES filter membrane according to the invention using colloidal gold;

FIG. 17 is a Scanning Electron Microscope (SEM) image of the cross section of a multi-layer composite ultrafiltration membrane prepared in patent CN 1759924B;

FIG. 18 is a schematic diagram of a compounding device in the preparation of a multi-layer composite ultrafiltration membrane according to patent CN 1759924B.

Detailed Description

In order to more clearly explain the overall concept of the present application, the following detailed description is given by way of example. In the following examples, raw materials and equipment for preparing the filtration membranes were commercially available, unless otherwise specified. Wherein the structural morphology of the filter membrane is characterized by adopting a scanning electron microscope with the model number of S-5500 provided by Hitachi company.

Example 1

A preparation method of an asymmetric PES filter membrane for virus removal comprises the following steps:

s1: preparing a casting solution, and casting the casting solution on a carrier to form a liquid film; wherein the casting solution comprises the following substances in parts by weight: 20 parts of polyether sulfone; 75 parts of an organic solvent; 20 parts of polar additive; the viscosity of the casting solution is 7500 cps; the organic solvent is dimethylformamide; the polar additive is a mixture of glycerol, azodimethyl N-2-hydroxybutyl propionamide and polyvinyl alcohol, and the mass ratio of the mixture is 2:1: 1;

s2: immersing the liquid film together with the carrier into the curing liquid for 40 seconds, wherein the curing liquid is immersed into the liquid film and gradually diffuses inwards, and then is cured to form a separation layer and a pre-filtering layer; the curing liquid comprises water and osmotic additive isopropanol, and the content of the osmotic additive is 50%; wherein the temperature of the curing liquid is 35 ℃ and the temperature of the carrier is 20 ℃.

Example 2

s1: preparing a casting solution, and casting the casting solution on a carrier to form a liquid film; wherein the casting solution comprises the following substances in parts by weight: 21 parts of polyether sulfone; 70 parts of an organic solvent; 18 parts of polar additive; the viscosity of the casting solution is 8000 cps; the organic solvent is N-ethyl pyrrolidone; the polar additive is a mixture of glycerol, azodimethyl N-2-hydroxybutyl propionamide and polyvinyl alcohol, and the mass ratio of the mixture is 2:1: 1;

s2: immersing the liquid film together with the carrier into the curing liquid for 45 seconds, wherein the curing liquid is immersed into the liquid film and gradually diffuses inwards, and then is cured to form a separation layer and a pre-filtering layer; the solidifying liquid comprises water and osmotic additive ethanol, and the content of the osmotic additive is 55%; the curing liquid temperature was 30 ℃ and the vehicle temperature was 15 ℃.

Example 3

s1: preparing a casting solution, and casting the casting solution on a carrier to form a liquid film; wherein the casting solution comprises the following substances in parts by weight: 23 parts of polyether sulfone; 65 parts of an organic solvent; 16 parts of a polar additive; the viscosity of the casting solution is 9000 cps; the organic solvent is N-methyl pyrrolidone; the polar additive is a mixture of glycerol, azodimethyl N-2-hydroxybutyl propionamide and polyvinyl alcohol, and the mass ratio of the mixture is 2:1: 1;

s2: immersing the liquid film together with the carrier into the curing liquid for 50 seconds, wherein the curing liquid invades into the liquid film and gradually diffuses inwards, and then curing to form a separation layer and a pre-filtering layer; the curing liquid comprises water and osmotic additive glycol, and the content of the osmotic additive is 60%; the temperature of the curing liquid was 30 ℃ and the temperature of the carrier was 10 ℃.

Example 4

s1: preparing a casting solution, and casting the casting solution on a carrier to form a liquid film; wherein the casting solution comprises the following substances in parts by weight: 15 parts of polyether sulfone; 85 parts of an organic solvent; 10 parts of polar additive; the viscosity of the casting solution is 5500 cps; the organic solvent is N-ethyl pyrrolidone; the polar additive is a mixture of glycerol, azodimethyl N-2-hydroxybutyl propionamide and polyvinyl alcohol, and the mass ratio of the mixture is 2:1: 1;

s2: immersing the liquid film together with the carrier into the curing liquid for 20 seconds, wherein the curing liquid is immersed into the liquid film and gradually diffuses inwards, and then is cured to form a separation layer and a pre-filtering layer; the curing liquid comprises water and osmotic additive isopropanol, and the content of the osmotic additive is 35%; the temperature of the curing liquid is 45 ℃, and the temperature of the carrier is 35 ℃.

Example 5

s1: preparing a casting solution, and casting the casting solution on a carrier to form a liquid film; wherein the casting solution comprises the following substances in parts by weight: 17 parts of polyether sulfone; 83 parts of an organic solvent; 12 parts of polar additive; the viscosity of the casting solution is 6000 cps; the organic solvent is dimethyl sulfoxide; the polar additive is a mixture of glycerol, azodimethyl N-2-hydroxybutyl propionamide and polyvinyl alcohol, and the mass ratio of the mixture is 2:1: 1;

s2: immersing the liquid film together with the carrier into the curing liquid for 25 seconds, wherein the curing liquid invades into the liquid film and gradually diffuses inwards, and then curing to form a separation layer and a pre-filtering layer; the solidifying liquid comprises water and osmotic additive ethanol, and the content of the osmotic additive is 40%; the temperature of the curing liquid is 40 ℃, and the temperature of the carrier is 30 ℃.

Example 6

s1: preparing a casting solution, and casting the casting solution on a carrier to form a liquid film; wherein the casting solution comprises the following substances in parts by weight: 19 parts of polyether sulfone; 81 parts of an organic solvent; 14 parts of polar additive; the viscosity of the casting solution is 7000 cps; the organic solvent is butyl lactate; the polar additive is a mixture of glycerol, azodimethyl N-2-hydroxybutyl propionamide and polyvinyl alcohol, and the mass ratio of the mixture is 2:1: 1;

s2: immersing the liquid film together with the carrier into the curing liquid for 30 seconds, wherein the curing liquid is immersed into the liquid film and gradually diffuses inwards, and then is cured to form a separation layer and a pre-filtering layer; the curing liquid comprises water and osmotic additive glycol, and the content of the osmotic additive is 45%; the curing liquid temperature was 35 ℃ and the vehicle temperature was 25 ℃.

Firstly, the method comprises the following steps: structural characterization

Carrying out morphology characterization on the membrane structure of the nanoscale polymer filtering membrane obtained in each embodiment by using a scanning electron microscope, and then obtaining required data; the specific results are as follows:

table 1:

table 2-PES filter body:

	thickness/mum	Porosity/%	PMI mean pore diameter/nm
				Example 1	85	76.2	20.7
Example 2	100	75.7	21.6
				Example 3	110	74.4	22.8
Example 4	50	77.5	16.4
				Example 5	60	79.2	18.3
Example 6	70	81.3	19.1

Table 3-separation and pre-filtration layers:

table 4-transition and cortical regions:

as can be seen from tables 1-4, the PES filter membranes prepared in the embodiments 1-6 of the invention all have ideal membrane structures, and the filter membranes are integrated into a membrane, so that the composite process is not adopted, and the process preparation is simple; the PES filter membrane is an asymmetric membrane, the pore diameter of the membrane pore changes along with the small thickness in a gradient manner, no extra large pore exists, the efficient interception of the virus is ensured, the flux is high, and the PES filter membrane is suitable for being applied to the field of virus removal.

Characteristic features

The membrane flux is calculated as follows:

the formula for calculating the membrane flux (J) is: j ═ V/(T × a) formula wherein:

j- -Membrane flux Unit: l H-1 m-2

V- -sample volume (L); t- -sampling time (h); a- -effective area of film (m2)

The PES filter membrane separation performance measurement adopts the following operating conditions: the feed liquid is deionized water, the operating pressure is 30psi, the operating temperature is 25 ℃, and the pH of the solution is 7; the throughput testing apparatus is shown in fig. 15;

	tensile strength/MPa	Elongation at break/%	flux/L h-1 m-2@30psi
				Example 1	7.5	19	1000
Example 2	8.5	15	840
				Example 3	9.5	11	700
Example 4	5.5	27	1320
				Example 5	6	25	1240
Example 6	6.5	23	1160

Furthermore, the following test methods were used in accordance with CN 201010154974.7-ultrafiltration membrane and its preparation method, paragraph 114: performing a virus retention test:

the virus used is a murine parvovirus with a particle size of 20 nm;

after tests, the PES filters prepared in examples 1-6 have an LRV of not less than 4 for virus impurities with a particle size of 20nm, thereby indicating that the PES filters of the invention have sufficient retention effect on viruses with a particle size of 20nm and above; and the protein yield of the PES filter membrane is not lower than 98 percent; the PES filter is therefore particularly suitable for use in the field of virus removal.

And (3) testing the filtering precision: testing the interception efficiency of the PES filter membrane obtained in each example; intercepting particles: colloidal gold experimental equipment with the particle size of 20 nm: a Tianjin Roots particle counter KB-3; preparation of the experiment: the experimental set-up was assembled as in fig. 16, ensuring the set-up was clean, and the set-up was rinsed with ultra-pure water; and a filter membrane with the diameter of 47mm is taken and arranged in the butterfly filter, so that the air tightness of the assembled filter is ensured to be good.

The experimental steps are as follows:

the challenge was poured into a tank, the butterfly filter was vented, pressurized to 10kPa, and a clean bottle was used to take the butterfly downstream filtrate.

The number of particles in the filtrate and stock solutions was measured using a particle counter.

Intercepting efficiency:

in the formula:

eta-type-interception efficiency,%;

n₀-number of particles in stock solution, average of 5 sets of counts;

n₁-number of particles in filtrate, average of 5 groups of counts, one.

After testing, the retaining efficiency of the examples 1-6 to the colloidal gold of 20nm is not lower than 99.99%.

The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may occur to those skilled in the art without departing from the principle of the invention, and are considered to be within the scope of the invention.

Claims

1. An asymmetric PES filter membrane for removing viruses, comprising a body having therein a non-directional tortuous path, one surface of said body being a first outer surface and the other surface of said body being a second outer surface, characterized in that: the average pore diameter of the first outer surface is 150-450nm, and the average pore diameter of the second outer surface is 10-42 nm;

2. An asymmetric PES filter for virus removal as claimed in claim 1, wherein: the first outer surface is provided with a plurality of first holes in a circular hole shape; the area ratio of the first holes on the first outer surface is 0.1-15%;

3. An asymmetric PES filter for virus removal as claimed in claim 1, wherein:

the average pore diameter variation gradient of the filter membrane is 1.5-6 mu m/1 mu m;

the ratio of the average pore size of the first outer surface to the average pore size of the second outer surface is 7-23.

4. An asymmetric PES filter for virus removal as claimed in claim 1, wherein: the PMI average pore diameter of the filter membrane is 15-25nm, the thickness of the filter membrane is 40-150 mu m, and the porosity is 70-85%.

5. An asymmetric PES filter for virus removal as claimed in claim 1, wherein: the PMI average pore diameter of the pre-filtering layer is 50-200nm, and the porosity is 75-93%; the thickness of the prefilter layer accounts for 70-90% of the thickness of the membrane.

6. An asymmetric PES filter for virus removal as claimed in claim 1, wherein: the pre-filtering layer comprises a skin layer area and a pre-filtering area; one side of the leather layer region comprises a first outer surface, the hole area rate of the first holes on the first outer surface is smaller than the hole area rate of the second holes on the second outer surface, and the thickness of the leather layer region is 0.3-3.2 um; the first holes have a hole area ratio of 0.15% to 1.5% on the first outer surface.

7. An asymmetric PES filter for virus removal as claimed in claim 1, wherein: the average pore diameter of the separation layer is 15-25nm, the porosity is 60-80%, and the thickness of the separation layer is 2-20 μm.

8. An asymmetric PES filter for virus removal as claimed in claim 1, wherein: the ratio of the average pore size of the pre-filtering layer to the average pore size of the separating layer is 4-13: 1.

9. an asymmetric PES filter for virus removal as claimed in claim 1, wherein: the pre-filter layer comprises first fibers forming a porous structure, and the first fibers are sheet-like structures; the separation layer comprises second fibers forming a porous structure, and the second fibers are in a strip-shaped structure; the first fibers have an average diameter greater than an average diameter of the second fibers, and the second fibers have an average diameter of 30 to 75 nm.

10. An asymmetric PES filter for virus removal as claimed in claim 9, wherein: the pre-filtering layer also comprises a transition area, the transition area is positioned on one side of the pre-filtering layer close to the separating layer, the continuous fibers form a porous structure of the transition area, and the continuous fibers gradually change from a sheet structure to a strip structure; one side of the continuous fibers adjacent the separation layer is continuous with one side of the second fibers adjacent the pre-filter layer.

11. The asymmetric PES filter according to claim 10, wherein: the average pore diameter of the transition region is 60-170nm, and the porosity is 75% -82%; the thickness of the transition zone is 4-20 μm.

12. An asymmetric PES filter for virus removal as claimed in claim 1, wherein: the tensile strength of the PES filter membrane is 5-10MPa, and the elongation at break is 8-30%;

the flux of the PES filter membrane is more than 600L x h^-1*m^-2@30psi；

The LRV of the PES filter membrane to virus impurities is not lower than 4;

the protein yield of the PES filter membrane is not lower than 98%.

13. The method for preparing an asymmetric PES filter membrane for virus removal according to any one of claims 1-12, comprising the steps of:

14. The method of claim 13, wherein the organic solvent is at least one of butyl lactate, dimethyl sulfoxide, dimethylformamide, caprolactam, methyl acetate, ethyl acetate, N-ethylpyrrolidone, dimethylacetamide, and N-methylpyrrolidone;

15. The method as claimed in claim 13, wherein the osmotic additive is at least one of isopropanol, ethanol and ethylene glycol.

16. The method of claim 13, wherein the temperature of the carrier is at least 5 ℃ lower than the temperature of the immobilized solution.

17. The method for preparing an asymmetric PES filter membrane for removing viruses as claimed in claim 16, wherein the temperature of the curing solution is 25-50 ℃ and the temperature of the carrier is 0-40 ℃.